Hillary Clinton flew out of Asia on Saturday after a trip dominated by significantly warmer ties with Myanmar as Washington looks to open the resource-rich former pariah to US firms.

The US Secretary of State held landmark talks with Myanmar President Thein Sein on Friday at a major business conference in the Cambodian town of Siem Reap, two days after the US gave the green light to investment in the country, including in oil and gas.

Clinton hailed changes in Myanmar as it emerges from nearly half a century of army rule and insisted that Washington had put in place "protections to ensure that increased American investment advances the reform process".

US firms will have to report on accountability issues, but rights groups have raised concerns that Washington is moving too fast to cash in on Myanmar's huge business potential.

Clinton's southeast Asian tour also included a regional security forum, as the US seeks to bolster Asian alliances to balance China's might, while avoiding overly antagonising Beijing.

On Thursday Clinton and her Chinese counterpart Yang Jiechi pledged to work more closely together.

The US Secretary of State sought to avoid being drawn into a host of maritime territorial spats between Beijing and many of its neighbours, but did express alarm at the potential for escalating tensions.

The US called this week for the Association of Southeast Asian Nations bloc to unify to negotiate with China, but deep splits among member states saw the group's regional summit end in failure to agree a joint statement.

Clinton on Saturday will head to Cairo, where she is due to hold talks with the country's new President Mohamed Morsi, after he locked horns with the powerful military.

Earlier this week Clinton urged dialogue between all parties amid wrangling between Egypt's new civilian leader and the generals who took charge after president Hosni Mubarak's overthrow early last year.

The Egyptian people should "get what they protested for and what they voted for, which is a fully-elected government making the decisions for the country going forward", she added.

Morsi on Wednesday said he would respect a court ruling overturning his decree for the dissolved Islamist-dominated parliament to convene.

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